The present invention relates to an information reproducing apparatus using a recording medium which holds information by using reversed magnetic domains on a vertical magnetic recording film formed on a substrate surface, and reproducing information by detecting magnetic leakage flux emerging from the recording medium. Or the present invention relates to an information recording apparatus using a recording medium which holds information by using a reversed magnetic domain on a vertical magnetic recording film formed on a substrate surface, recording information by forming reversed magnetic domains, and reproducing information by detecting magnetic leakage flux emerging from the recording medium.
In a conventional information recording medium and its recording apparatus (prior art) capable of conducting both optical magnetic reproduction and magnetic reproduction as described in JP-A-10-21598, recording was conducted by applying recording light from a light source to an optical magnetic recording film formed on a recording medium, through a substrate, thereby heating the optical magnetic recording film, and forming a reversed magnetic domain. Furthermore, information reproduction was conducted by applying reproducing light from the light source to the above described optical magnetic recording film through the substrate and detecting rotation of polarization plane of reflected light, and forming a second magnetic layer on the optical magnetic recording film and conducting leakage flux reproduction from the second magnetic layer.
In the conventional technique, the light source was disposed across the substrate from the recording film. As a result, it was impossible to form recording films on both surfaces of the substrate and conduct recording. Furthermore, since the substrate must have transparency with respect to the wavelength of the light source, the degree of freedom with regard to the material of the substrate was low and a thin inexpensive substrate having an excellent mechanical property could not be used. In addition, it was necessary to separately prepare means for positioning a recording means and a reproducing means in arbitrary positions on the recording medium. Therefore, there were disadvantages as regards apparatus size, cost, and recording medium cost.
Furthermore, the tolerance was narrow as regards the thickness error of the substrate and the error of the angle formed between the substrate and the optical axis. It was thus necessary to keep high mechanical precision of the information recording apparatus and recording medium. This resulted in a disadvantage with regard to the apparatus fabrication cost.
In order to solve the above described problem, the present invention provides an information recording apparatus using a recording medium which holds information by means of reversed magnetic domains on a perpendicular magnetic recording film, the information recording apparatus including:
an irradiation means for applying electromagnetic energy or light to the recording medium; and
a magnetic flux detection means for detecting magnetic leakage flux emerging from the recording medium, the magnetic flux detection means being disposed on the same side as the irradiation means with respect to the recording medium.
As a result, double-sided-recording on the recording medium can be conducted. In other words, data simply twice as much as data of the conventional technique can be recorded. Although electromagnetic energy or light is applied here, any one may be used so long as it locally excites the recording medium by focusing with, for example, a lens. As examples of electromagnetic energy or light, there are infrared light, ultraviolet light, and so on besides visible light.
Furthermore, the information recording apparatus further includes a slider for scanning the recording medium surface with at least a part of the irradiation means and the magnetic flux detection means being mounted on the slider. It has thus become possible to simultaneously adjust the irradiation position and the magnetic flux detection position.
Furthermore, at least a part of the irradiation means of the slider is disposed ahead of the magnetic flux detection means in the scanning direction. It has thus become possible to dispose the irradiation means which may have a somewhat large flying height ahead of the magnetic flux detection means, and dispose the magnetic flux detection means desired to have a reduced flying height nearer the recording medium.
Furthermore, a SIL as at least a part of the irradiation means is mounted on the slider. Thus the slider is disposed closer to the recording film, and magnetic flux detection has been facilitated. Furthermore, owing to the SIL, it has become possible to form minuter record marks with the same light source wavelength.
Furthermore, an objective lens as at least a part of the irradiation means is mounted on the slider. The irradiation position is made movable simultaneously so as to correspond to the magnetic flux detection position.
Furthermore, an optical fiber as at least a part of the irradiation means is mounted on the slider. It has been attempted to reduce the weight of the irradiation means, and access performance has been improved.
Furthermore, a lens actuator for adjusting the position of the objective lens is mounted on the slider. It has thus been made possible to adjust the relative position of the objective lens with respect to a magnetic flux detection device finely.
As for this adjustment, it can be also be conducted by mounting an actuator for adjusting the relative position relation between a focused position of the electromagnetic energy or light on the recording medium and the magnetic flux detection means.
Furthermore, the information recording apparatus includes a recording magnetic field applying means for applying a recording magnetic field to the focused position of the electromagnetic energy or light on the recording medium. Since the size of the record mark is determined by the size of the spot irrespective of the magnetic field application range by the magnetic field applying means, the size of the mark is considerably small. As for the magnetic field direction at this time, the recording density is larger in a direction perpendicular to a main surface of the recording medium than in a longitudinal direction.
In the present invention, light can be used exclusively for recording, and consequently polarization direction detection in conventional magneto-optical reproduction becomes unnecessary. By using a polarization beam splitter having a transmission factor from the light source to the recording medium equivalent to almost 100% and a reflection factor equivalent to almost 0%, therefore, the utilization efficiency of light can be made higher.
Furthermore, another aspect of the present invention provides an information recording apparatus including a light irradiation position control means for controlling a light irradiation position by using reflected light from an embossed structure portion provided on a surface of a recording medium, and
a magnetic flux detection position control means for detecting magnetic leakage flux in the embossed structure portion and controlling a position of magnetic flux detection. Therefore, the embossed structure can be used in common for position control of both light irradiation position and magnetic flux detection position.
Furthermore, as another aspect of the invention, an crescent-shaped magnetic domain is formed in magneto-optical recording of a magnetic field modulation method. Therefore, highly efficient reproduction has been realized by providing a magnetic flux detection means having substantially arc-shaped magnetic flux detection sensitivity distribution along the recording medium surface.
By the way, as a secondary effect, it becomes unnecessary for the substrate of the recording medium to have transparency with regard to the wavelength of the light source. Accordingly, the degree of freedom with regard to the substrate material becomes high. It thus becomes possible to use a thin inexpensive substrate having an excellent mechanical property. As a result, there are extreme advantages as regards apparatus size and recording medium cost.
Furthermore, since the focusing route of energy does not pass through the substrate, the problem of the thickness error of the substrate is solved, and simultaneously therewith the tolerance with regard to the error of the angle formed between the substrate and the optical axis is widened. Therefore, the mechanical precision of the information recording apparatus and the recording medium can be relaxed, and there are extreme advantages as regards the apparatus fabrication cost.